Dissections occur when the wall of a lumen tears, creating a secondary or false lumen. Blood can flow into this false lumen, generally causing the vessel to balloon outwardly as a result of the weaker lumen wall. If the dissection is left untreated, there is the risk of rupture of the lumen, with severe consequences to the patient. Dissections can be treated by open surgery, involving closing the tear by suturing and/or strengthening of the lumen wall, again often by suturing. Open surgery procedures should, however, preferably avoided, particularly to the thoracic region, in light of the trauma caused to the patient. For this purpose, some endoluminal treatments have been developed in which the dissection is treated by means of a stent or stent graft placed against the damaged portion of the vessel wall. The stent or stent graft acts to press together the two parts of the lumen wall so as to close off the false lumen. It have been found that if the false lumen can be closed, the lumen wall often repairs itself. A stent graft can usefully be placed at the point of the tear, so as to close off the blood supply to the false lumen. This removes the blood pressure in the false lumen and thus allows the two parts of the lumen wall to come into contact one another and thus to heal in time.
The use of stents and stent grafts to treat dissections has been restricted to lumen locations and zones which are free of complications, such as branch vessels, complex lumen geometries and so on, particularly in light of the difficulties in placing the stent and stent grafts accurately in the lumen. As a result of the particular complexities of Type-A dissections, that is dissections in the ascending aorta, stents or stent grafts have not been used. At this location, there is only a short length of aorta which is free of side branches critical to the health of the patient. The geometry of the lumen, that is beyond the aortic arch, also causes positioning difficulties For these reasons the treatment of Type-A dissections still remains restricted to open surgical procedures.